Specifying Liquid Silicone Medical Rubber Parts
The following are some of the specification items. How demanding the specification determines the cost of the tooling and parts.
| Material Supplier and Material: |
Example: Wacker 303060 |
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| Durometer – (with value): |
Example: Shore A 60 Durometer |
| Color: |
Typical choices are clear, transparent, color match for tint, solid color. Include color dispersion manufacture product number and percent color. |
| Part Identification: |
Laser marking or ink marking. |
| Dimensional Tolerances: |
Typical from +/- of .002inch or +/- 0.051 mm to +/- .005 inch or +/- 0.127 mm. Note: in specifying tolerance of a silicone rubber part method of measuring the part tolerances should be considered. |
| Flash Tolerances: |
When the two halves of a mold come together there will be flash. It might not be visible without magnification. Typical flash tolerances for parts are projection down to 0.002inches / 0.127 mm and flash thickness of 0.003 inches to 0.0076 mm and up to what can be tolerated. |
| Mitre Tolerances: |
(Mold Miss Match) Alignment of the two mold halves if critical should be specified could affect wall tolerances. Typical mitre could be tolerance of +/- of .002 inch or +/-0.051 mm. |
| Air Bubbles: |
Can effect part performance and vary from no visible to not visible under value of magnification. |
| Contamination: |
Surface and part vary from no visible to not visible under value of magnification. |
| Post Baking: |
Is important for medical application so that all cross-linking is completed. If cross-linking is not completed possible part will produce volatiles as it completes cross-linking. Post baking time and temperature relates to max part cross-section. |
| Packaging: |
Should be double poly bagged and each bag sealed, and labeled. |
| Validation: |
Should include material certification and your requirements. |
Strongly recommended to:
- Determine the correct silicone material for the properties required.
- Choose a durometer and mold parts in that durometer and higher and lower value—note different durometers and manufactures effect the shrink.
- Check Fits.
- Determine shrink values for part.
- Reduce risk in building production tool.
